Interpretation: Seasons are defined as months in this plot. Each sub series depicts the variation in flow for each month over different years. There are peaks when snow melts and lows in dryer or colder times of the year.
There is long term changes in flow possibly due to climate change or land use changes. This can be seen in the trend section of the graph. Also seasonal changes can be seen in the peaks in flow throughout the year with peaks and valleys. The remainder captures anything irregular with the data.